1. Field of the Invention
The present invention concerns a weighing and portioning technique based on the so-called grader technique, where a number of items which are to be portioned out, namely natural foodstuff items with varying weight, are subjected to a weighing-in and are thereafter selectively fed together in a computer-controlled manner to receiving stations for the building-up of weight-determined portions in these stations. In accordance with the known practice, this is effected by a weighing-in on dynamic scales and a subsequent transport along a sorting-out track with control means which can be activated in a selective manner for the delivery of the items to the respective receiver stations along this track.
With the invention it has been realised that use can be made, with very attractive consequences, of a radically changed technique for carrying out both the relevant task and various related operations, namely by not only effecting the delivery, but preferably also the weighing-in while making use of the gradually highly- and commercially-developed robot technique.
2. Description of Related Art
Especially with the use of vision equipment, it is an easy task for a robot arm to grip a conveyed item in a delivery area, e.g. with a suction cup, and feed the item to any receiving station within the operational range of the robot arm. This can be effected immediately if the item has already been weighed and its position determined with regard to the receiving station, and thus these stations do not have to be physically disposed in any certain pattern such as along a conveyor belt, regardless of whether a certain row disposition can be practical out of regard for the guiding-out and feeding away of the formed portions.
However, it is an important aspect of the invention that the robot arm in itself can be arranged not only to grip the items, but also to determine the weight of a supplied item already during an initial lifting of the item from its under layer. This can be effected in a direct manner by mounting the gripping tool on the robot arm in connection with a weighing cell and preferably also an accelerometer, so that a weighing can be effected during an uneven movement, preferably by an initial vertical lifting, so that the weight determination and allocation of the item can be carried out when the item is lifted to a height from which there is initiated a bringing-out of the item in a direction towards the selected receiving station, including a swinging.-out for the execution of a movement along one or more e.g. circular rows of receiving stations. The weight determination can also be effected in a less direct manner, e.g. by use of a vision system which, in connection with the lifting of the item, is now also given access for a detection of the underside of the item, whereby the weight can be determined with an accuracy which can be sufficient in many connections. An indirect weight determination can also be effected by the robot arm being influenced with a carefully controlled lifting moment, which will be opposed by the inertia of the item, whereby with a moment analysis of the lifting sequence an expression for the item weight can be calculated.
With the use of vision equipment for place determination of arriving items in connection with the robot-based weight determination of the gripped items, there arises a distinct changing of the conditions which have hitherto been valid for the function of the grading machines. This function has hitherto been conditional on the arriving items being fed individually to the dynamic weighing station, and thereafter conveyed individually, i.e. with suitable distance between them, along the sorting-out track, which hereafter will not apply. The vision equipment can monitor a relatively long and broad supply area at which the items can arrive both at the side of each other and without any critical separation, neither in breadth nor lengthways direction, in that the robot arm can nevertheless drop down with great precision on any selected item. It will be a further possibility that the vision equipment can monitor up to several candidate items in seeking for an item of a certain precise weight, e.g. for the conclusion of a building-up of a portion to a fixed weight. If the vision equipment in itself is not able to effect a weight determination with the necessary accuracy, it will still, however, be able to weigh the items in a “weight-class-determined” manner, and thus hereby disclose e.g. 2-4 items which, with good probability, can be so close to the sought-after weight that one of the items will in any case be able to be used for the purpose. There can thus be effected a more accurate weight determination by the operative robot carrying out a control-weighing of these selected items, and hereby either select the best candidate or omit to use any of them.
To this can be added that by use of the vision equipment, there can also be effected a type determination of items which are supplied in mixed type formation, e.g. in the form of different pieces of parted chickens. In certain productions this will be a quite important criterion for the allocation of the items.
It must be emphasised, however, that it will not be any precondition that use be made of vision equipment, in that it has been found possible to let a robot gripping element fetch items from an area with closely-grouped items. The gripping element can possibly be arranged with a sensor for registration of a failure to grip any item, after which it can be immediately moved slightly for a new attempt.
In the handling of items such as whole fish or chicken legs (“drumsticks”), which are desired to be received at each of the receiving stations in oppositely-directed orientations so that they can be placed together in close formation, or that they can be built up in a receiving box in portions in several layers for achieving a more-or-less horizontal upper layer in the box filling, the control unit will easily be able to be instructed whether the robot arm's gripping tool is to be influenced, if necessary, to turn the gripped item through such an angle that will be suitable for ensuring that the item, upon delivery to the receiving station, will have an orientation which accommodates the relevant requirement on the basis of the information which already exists in the control computer.
Furthermore, with the invention it will be a possibility that “the system”, i.e. the controlling of the robot arm, is programmed so that from time to time, and e.g. especially after each working day, the robot arm's gripping tool is controlled for gripping a cleaning nozzle or hose, by means of which the apparatus can thereafter clean itself and all the receiving stations. Finally, the gripping tool itself can be cleaned by co-operation with a stationary cleaning nozzle.
There is hitherto considered a weight-determined portioning-out, but the technique will have further possibilities such as a pure sorting-out of items in accordance with more or less any criterion, which shall not necessarily involve a weight criterion, e.g. in accordance with type, colour, shape, degree of possible deformation etc.
The technique can also be used for the distribution of items out to a group of receiving stations, in which the received items are weighed separately with the view to feeding them together in weight-determined portions on the basis of the so-called combination-weight principle.
In the laying-out of items on a packing element, such as slices of salmon on a cardboard plate, or the laying-out of items in assortment boxes, it will be a possibility that there has been laid an item which proves to be able to be replaced by a more suitable item, and here there will be the special possibility both that the items can be placed in special patterns, e.g. by scale layout or at the side of one another, and that the robot can be directed by the control unit to remove the “wrong” item from the under layer in favour of the laying-out of an even better item.
It is mentioned that in the supply area to the robot there can appear a relatively large number of items which can be gripped selectively, possibly even by more than a single robot. It can hereby arise that a deficit of items of one or more different qualities can be registered, e.g. in type or size, which are awaited for the furthering of a quick portioning-out. In this connection, it is a possibility that work can be effected with a supply area coupled up front, possibly even of increased size, where one or more robots work in a corresponding manner for the selective transfer of relevant items to the operative supply area.
If the operative robot arm grips an item which after weight determination is not suitable for placing in any of the receiving stations, it can deliver the item either to a re-circulation station or merely back to the supply area, or to a special parking area for items already weight determined, which are thus ready for selective collection at the first given opportunity during the further sequence.
Such a “parking area” can also be used operatively by one or more of the robots being used to receive and to carry out the weight determination of the supplied items, and thereafter deliver the items in a parking area during registration of the respective positions and weights. Hereafter, the only task to be carried out by the operation robot will to distribute the items out to the receiving stations, i.e. it can be without weighing means and without vision equipment, and it can work at increased speed in that the weighing function is omitted. In the parking area, the items can be placed closely at the sides of one another, i.e. operations can be effected with a quite large number of candidates for portioning-out.
When work is to be carried out with the desirable, relatively fast operation frequencies, it can be quite difficult to arrange weighing equipment in connection with a robot arm. It has already been mentioned that the weighing can well be effected by an intermediate delivery of the items to a static weighing device, but this will inevitably result in an increase in the cycle time, since at each weighing there will arise both an in-swinging period and a weighing period, and since none of these can be integrated with an operative movement of items, both of these periods, regardless of whether they can be of short duration, will have a delaying effect on a quick handling of the items. In light of this, it is a special feature of the invention that it can work with “negative weighing”, namely in that newly arrived items can be fed successively to a static weighing device or buffer scales which register the weight of that or those items which are placed on the scales, in that the weight determination of an item, which is then gripped and removed by the robot arm can hereby be registered by the associated reduction in the weight on the scales. The said swinging-in and weighing sequences can hereby be concluded already before the relevant item is gripped and removed, and even though a renewed swinging-in and weighing period must subsequently be accepted for determination of the weight of the removed item, this can thus be effected during the actual initial movement of the gripped item, and consequently integrated anyway with this movement without delaying the movement.
In the foregoing it is intimated that the “robot arm” moves in a pivoting movement, regardless of whether the robot otherwise or also moves in diverse horizontal directions, and here it must merely be emphasised that the invention will not be limited in a corresponding manner, the reason being that the robot arm, with its related gripping element, can be displaced just as well as a fixed arm on a robot structure, which as an integrated whole moves in a controlled, co-ordinate-related manner in a length/breadth-controlled operating system.
In the following, the invention will be described in more detail precisely on the basis of such a co-ordinate-related system, without this excluding a pivoting system, and moreover with reference to the drawing, in which